Hitherto, glass antennas for receiving AM radio broadcast waves and FM radio broadcast waves have higher gain as an area surrounded by antenna strips increases. Therefore, these glass antennas are often provided on the rear window glass of the automobile which is easy to ensure a large area for obtaining a good reception gain. The rear window glass of the automobile is often formed on its central region with defogging heater strips for ensuring rear visibility at the driving in rain. Therefore, in a case in which the glass antenna is formed on the rear window glass, it has been forced to be formed on the blank space of the peripheral portions of the defogging heater strips, especially, the blank spaces above or below the defogging heater strips.
Moreover, the horizontal strips, the vertical strips and so on of the antenna provided around the defogging heater strips were often adjacent to the heater horizontal strips, the bus bars and so on of the defogging heater strips. With this, it was possible to use the radio wave received by the defogging heater strips as the antenna, and to improve the reception gain.
For example, Japanese Patent Application Publication No. 2003-78319 (patent document 1) discloses an automotive glass antenna including defogging heater strips which are provided on a rear window glass, and which has a plurality of heating conductive strips, and bus bars connected with ends of the plurality of the heating conductive strips. This glass antenna includes a feed point provided in a peripheral portion of the glass in blank spaces above or below the defogging heater strips; a first element including at least a first horizontal strip which extends from the feed point, and which achieves the capacitive coupling with the heating conductive strips; and a second element including a vertical strip which extends from the feed point, which is disposed outside the bus bar, and which is connected with the bus bar at an end of the vertical strip or by branching from a middle portion of the vertical strip.
Moreover, Japanese Patent Application Publication No. 5-251918 (patent document 2) discloses an automotive glass antenna including a first antenna including horizontal strips and vertical strips provided in a space above defogging heater strips of an automotive rear window glass, and at least a second antenna including a first element which is connected with a feed point arranged in a lateral area under the defogging heater strips, which extends in the upward direction outside the defogging heater strips, and which further extends in the horizontal direction in a blank space above the first antenna or in a blank space of the first antenna; and a second element which is connected with the feed point, which extends in the horizontal direction in the blank space below the defogging heater strips, and which is folded to extend in the horizontal direction toward the feed point.    Patent Document 1: Japanese Patent Application Publication No. 2003-78319    Patent Document 2: Japanese Patent Application Publication No. 5-251918